Biology Cell Organelle Structure/Function Flashcards
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Read the first 7 Biology Cell Organelle Structure/Function flashcards as text
A researcher discovers a protein with a signal sequence targeting it to the mitochondrial matrix. Through which structure(s) must this protein pass after synthesis on cytoplasmic ribosomes?
Answer: Both the outer and inner mitochondrial membranes via translocases
Cytoplasmic proteins destined for the mitochondrial matrix must cross both the outer membrane (via TOM complex) and the inner membrane (via TIM23 complex) using translocase complexes.
Plasmodesmata in plant cells are functionally analogous to which structure in animal cells?
Answer: Gap junctions
Both plasmodesmata and gap junctions allow direct cytoplasmic communication between adjacent cells, enabling the passage of small molecules and ions.
Which organelle would be most abundant in a cell that secretes large amounts of digestive enzymes, such as a pancreatic acinar cell?
Answer: Rough ER and Golgi apparatus
Secretory proteins like digestive enzymes are synthesized on rough ER ribosomes, then processed and packaged in the Golgi for exocytosis.
The mitochondrial matrix contains all enzymes needed for which metabolic pathway?
Answer: The citric acid (Krebs) cycle
The enzymes of the citric acid cycle are located in the mitochondrial matrix, where they oxidize acetyl-CoA and generate NADH, FADH2, and CO2.
Which of the following is a key difference between prokaryotic and eukaryotic ribosomes?
Answer: Prokaryotes have 70S ribosomes; eukaryotes have 80S ribosomes
Prokaryotic ribosomes are 70S (50S + 30S subunits) while eukaryotic cytoplasmic ribosomes are 80S (60S + 40S subunits); this difference is exploited by many antibiotics.
A mutation destroys the proton gradient across the inner mitochondrial membrane. What would be the direct consequence?
Answer: ATP synthase could not produce ATP
ATP synthase uses the proton gradient (proton-motive force) as the driving force to synthesize ATP; without the gradient, ATP synthesis via oxidative phosphorylation would cease.
In the endomembrane system, vesicles traveling from the Golgi to the plasma membrane for exocytosis are called what?
Answer: Secretory vesicles
Secretory vesicles bud from the trans face of the Golgi apparatus and transport their cargo to the plasma membrane, where they fuse and release contents outside the cell.